I’m still having problems with my diff lock not engaging, I have the error code A2 on the dash. I replaced the solenoid on the front of the transmission down beside the drive shaft as recommended, the Terex book calls it a switch. When I order the solenoid terex sent me the wrong part, I received a valve solenoid. I kept what they ordered me but I got the correct solenoid for the transmission and installed it, I still don’t have a working diff lock. They said the valve solenoid they sent me the first time is also responsible for the functionality of the diff lock. The problem is I can’t figure out where it goes, I’ve looked in the book and studied the machine as best I can but I’m at a loss. The switch in the dash works and I have power down to the solenoid on the transmission but I’m Unfamiliar with working on this truck so I don’t know where to try next. While try to fine the valve solenoid I discover this solenoid on the back of the cab directly below the muffler was unplugged, any idea what it does?
Hi Jtf05, as far as I remember the TA 40 that date got a mechanical difflock in transmission, the newer, smaller TA 30 has powershift difflock. My initial misunderstanding, sorry. There is a hose going down to front side of transmission output, see pic. The difflock should be off (open, not engaged) with pressure at port 9, engaged w/o pressure. However with a "A2" code on display still something wrong with wiring, plug or solenoid. Removing hose to port should keep difflock engaged for test.
Thank you for your time, if the hose is removed do I just put a plug in it’s place? I’m only aware of two solenoids one on the front of transmission near the drive shaft which I have replaced and one on the center axle. It’s my understanding that there may be a third valve solenoid but I don’t know where it’s at. I have one that Terex sent me but they couldn’t tell me where it goes. I’ve looked at the wording harness but I don’t see anything wrong visually with plugs or wires.
Hi Jtf05, for testing a plug will do as there is no pressure around internal piston. A2 code: I'm not sure how the Terex guys actually wired the difflock system. Usually transmission difflock and center difflock mid and rear axle was shifted together. So they might have used to TCU output to fire both solenoids, maybe also via a relais. I'd assume the rear solenoid is also close to the body axles. TCU: pins 8 ad 53 provides the plus of 24 V, pin 11 provides the minus when difflock on. Which code is on display if you disconnect the plug of new solenoid? Should switch to code A3 with no further consumer.
Hi, bigbert I put plugs in two hoses the go into a T fitting at port 9 as you suggested to check the mechanical part of the diff lock. While operating the truck I had code WT and code C3 come up I’m just wonder what those mean. Also I thought about the fact I haven’t checked for power at my diff lock solenoid on my center axle, I don’t have any power there when I turn my switch on. I assume whatever is causing my lack of power on that plug is causing my A2 code to flash. I now have a light on in the dash and I’m not sure what it means so I will post them here also. I was able to fine the codes I listed above on line but I’m wonder why my torque converter would be getting hot so easily now. As soon as I plugged the hoses and started the truck it has been very sluggish as well.
Hi Jtf05, the WT is the warning level for overtemp. converter (approx. 115 C), C3 the fault level (5 degrees higher). Isn't there a gauge for t/m temp on dash? What does it show during converter heat? Gauge is sump temp. Lamp 13 should be on with difflock on, the switch below port 9 is the return signal for difflock. Did you ever check the wiring and plugs through cabin floor? This is usually the weak point of wiring. Lamp 3 is low pressure front axle brakes, these should recover during engine on. Will send you an operators manual for gearbox in email.
Hi, bigbert I have a gauge on the dash that says transmission temp and was only showing.80-90 degrees. I’m wondering if one of the two hoses I plugged going into the T at port 9 are causing the converter to over heat for some reason. No I haven’t checked the plugs coming into the cab as I didn’t know which pins to check, my plugs come through the front of the cab unless I’ve missed something. I checked the solenoid on my center axle for power yesterday and I didn’t have any, I’m assuming it get power from the same wire as the switch at port 9. Also as shown in one of my pictures I had a light on in the dash at number 15.
Hi Jtf05, yes please rebuild to old hosing to check how converter temp again is behaving. Usually the converter/cooler hoses are big size (approx. 35 mm inner dia, the difflock pipes 6 or 8 mm dia). Again, with no pressure at port 9, difflock of transmission should be engaged.
Ive only seen the TA-35's. When I would get the A2 diff lock code it was always a wiring issue. The exhaust piping on the 35's ran right next to the transmission wiring harness at the side of the transmission. The exhaust pipe started rusting and eventually would blow out a chuck of the exhaust pipe and burn the transmission harness. I'm not sure on your TA-40, but you really need to check ALL the wiring for the diff lock before you do anything else.